This invention relates to a shut-off valve that is used as a part of a filtration system of the type that has replacement filter cartridges with an integral tubular coupling member. When the filter cartridges are removed for replacement it is important that means be provided to prevent flow through the system if the filter cartridges are not replaced. That is, the shut-off valve of this disclosure is intended to provide a fail-safe arrangement for use in a filtration system employing removable filter cartridges so that in the event a workman removes a filter cartridge and fails to replace it, the system cannot be operated to pass fluid flow through it.
As an example of a filtration system that employs a fail-safe valve in a filtration vessel to prevent the flow of fluid through the filtration vessel in the event a filter element is removed and not replaced, reference may be had to co-pending U.S. Ser. No. 07/640,139 filed Jan. 11, 1991, which is now Pat. No. 5,122,264, entitled "Liquid Fuel Dispensing System With Improved Means Of Preventing Contamination". This previously filed application illustrates, at FIG. 8 therein, a type of adapter for telescopically and sealably receiving the tubular coupling member of a filter element. The adapter has a tubular valve element that is slidably positioned within an annular housing arranged such that until the valve element is physically displaced when a filter element coupling member is inserted into the adapter, fuel cannot flow therethrough. The present disclosure is for a device intended to accomplish the same result but having several improved features. An important difference in the device of the present disclosure compared to the fail-safe device of co-pending application Ser. No. 07/640,139, now U.S. Pat. No. 5,122,264, is that the device of the present disclosure is constructed in such a way that increased fluid pressure forces the valve more tightly towards the closed position.
For further background information relative to the present disclosure reference may be had to U.K. Patent GB 2 099 11 B entitled "Improvements In Or Relating To Shut-off Valves". This U.K. patent shows a type of shut-off valve to which the present disclosure is directed and is a further illustration of the environment in which the present disclosure is employed. The shut-off valve of the present disclosure, however, has improvements beyond those disclosed in the above-mentioned British patent. As an example, in the present disclosure the need for an elastomeric O-ring is eliminated. In addition, the present disclosure provides an arrangement having parallel seating surfaces within a tubular housing and in like manner on the exterior surface of a spool, so that the valve, in the closed position, provides dual sealing surfaces on opposite sides of outlet ports in the tubular housing.
Other important advantages of the shut-off valve of the present disclosure compared to that of the British patent are its simplicity and economy of construction and ease of assembly.